As the other posters have noted, it depends on your era and intended use. Unless you are modeling pre-WWII, the Mike would be my choice.
The Mikado basically took over as the heavy mainline loco on all Class I's by the 1920's. As steam evolved in the 30's and 40's, Mikes gradually were displaced from mainline service by larger/heavier steam, including 8-coupled engines like 2-8-4 Berkshires and 4-8-4 Northerns (or "Niagra's" if your an NYC person), or even heavier 2-10-4's and big articulateds like the Big Boy (UP only), Challenger, Allegheny, Yellowstone, N&W's Y's, etc. But Mikes hung around on most Class I's until the end of steam.
If you're modeling the transition era, say late 1940's to mid-50's, Mikes were much more common and used mostly in local/branch service, but could plausibly be put on a mainline through freight. Not many Consolidations were still on the road by by then. But up through WWII, almost all roads used Connies for a variety of tasks, mostly branchline and local service. And a few lasted nearly to the end of steam in the 50's.
John C.